Merging two m4v Movie Files Using AVMutableComposition - Videos Will Not Merge

Question

I am using the below code to try and merge two m4v files stored in the documents folder :

CMTime insertionPoint = kCMTimeZero;
NSError * error = nil;

AVMutableComposition *composition = [AVMutableComposition composition];

AVURLAsset* asset = [AVURLAsset URLAssetWithURL: [assetURLArray objectForKey:kIntroVideo] options:nil];

if (![composition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) 
                          ofAsset:asset 
                           atTime:insertionPoint 
                            error:&error]) 
{
    NSLog(@"error: %@",error);
}

insertionPoint = CMTimeAdd(insertionPoint, asset.duration);

AVURLAsset* asset2 = [AVURLAsset URLAssetWithURL: [assetURLArray objectForKey:kMainVideo] options:nil];

if (![composition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset2.duration) 
                          ofAsset:asset2 
                           atTime:insertionPoint 
                            error:&error]) 
{
    NSLog(@"error: %@",error);
}

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];

NSString *exportVideoPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/FinishedVideo.m4v"];

NSURL *exportURL = [NSURL fileURLWithPath:exportVideoPath];
exportSession.outputURL = exportURL;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
    switch (exportSession.status) {
        case AVAssetExportSessionStatusFailed:{
            NSLog (@"FAIL");
            break;
        }
        case AVAssetExportSessionStatusCompleted: {
            NSLog (@"SUCCESS");
}
};
 }]; 
}

The problem is that the two videos will not merge properly. The total merged movie duration is correct, however the video never transitions to the second movie and continues to display the last frame of the first movie for its duration. Oddly I can hear the audio for the second video playing in the background.

Does anyone have any ideas what is wrong ?

EDIT - The odd thing is is that if I merge two clips of exactly the same length it works.

EDIT - Have tried changing file extension to .mov with same problem.

Answer 1

You havent set the composition to the exportSession.

After the line:

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];

Add this line

exportSession.videoComposition = composition;

This should solve your problem.

Answer 2

Ok - so I eventually got this working by using individual AVMutableComposition tracks and then setting a mutablecomposition for audio and one for video.